As for degus, these eas easily maintained in an aquarium type setting. However you need to provide a solid running wheel and the tank needs to be more than 15 gallons. A twenty gallon would be sufficient for a pair. They also need to have branches to climb on and chew. They CANNOT have sugar because they cannot digest it, however apples they can have but in moderation. Sugar causes diabetes and also cataracts in degus.
You need to be very careful of their tail because it can be 'skinned" which means if you grab the tail the skin will slip. It will come off exposing the bone, flesh and muscle. You will then need to amputate it.

Hedeghogs also would fair fine in a tank. They need to stay very warm though because if they get too cold they can go into hybernation and die. You must not let your hedgehog get too cold. I provide an undertank heater during the winter time as well as lots of fluff and extra protein such as chicken and ground beef.

Duprasi can also be kept in a tank. Their tails are the same for the degu as well as gerbils, which I would also highly recommend. If you like the more exotic pets, maybe some zebra mice or spiny mice? Sugar gliders would not be a good idea because the need a tall wire cage which allows them to glide, one that can fit plenty of branches.

It is also a good idea that you get same sex pairs and also make sure you check with your local Fish and Wildlife to see whether keeping certain exotics are legal in your area. I would suggest getting the same sex for exotics because you need to be USDA licensed if you live in the US to sell or breed exotic pets.

But yes guinea pigs are also a good idea. What about a rabbit?